The aim of this research is to study the physiological and pharmacological properties of pinched-off mammalian brain presynaptic nerve terminals in vitro. The fate of synaptic vesicles is being examined by following vesicle membrane recycling with morphological markers sudh as horseradish peroxidase and colloidal thorium dioxide. Calcium transport and intra-terminal calcium sequestration is also being investigated - for example, we are endeavouring to determine where (in which organelles) calcium is sequestered. An effort is being made to isolate the protein(s) responsible for calcium transport across the plasma membrane. We would like to reconstitute this protein into a synthetic lipid vesicle system so that we can study the detailed kinetics and energetics of the transport processes, and determine how (at the molecular level) the ion translocation is carried out. BIBLIOGRAPHIC REFERENCES: Blaustein, M.P. Barbiturates block calcium uptake by stimulated and potassium-depolarized rat sympathetic ganglia. J. Pharmacol. Exp. Therap. 196: 80-86 (1976). Blaustein, M.P., and Ector, A.C. Carrier-mediated sodium-dependent and calcium-dependent calcium efflux from pinched-off presynaptic nerve terminals (synaptosomes) in vitro. Biochem. Biophys. Acta 419: 295-308 (1976).